JP2021102274A - Manufacturing method of thermoplastic fiber reinforced resin molded product - Google Patents

Abstract

To provide a method for obtaining a fiber reinforced resin molded product with high dimensional accuracy by press-molding a thermoplastic fiber reinforced resin.SOLUTION: A method for manufacturing a thermoplastic fiber reinforced resin molded product with a thickness of 0.2 to 5.0 mm by pressing one prepreg 3 of a thermoplastic fiber reinforced resin, a plurality of laminated prepregs, or a plurality of prepregs laminated by arranging an adhesive or an adhesive resin sheet between the prepregs includes: a step of raising temperatures of an upper mold 1 and a lower mold 4 to 170 to 270°C; a step of arranging the prepreg between the upper mold and the lower mold; a step of deforming the prepreg by applying a load to the prepreg; a step of lowering the temperatures of the upper mold and the lower mold at a rate of 5 to 50°C per minute; and a step of raising the temperature of the upper mold and taking out the thermoplastic fiber reinforced resin molded product after the upper mold and the lower mold are sufficiently cooled.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a thermoplastic fiber reinforced resin molded product by pressing a prepreg.

In recent years, due to environmental problems, efforts to improve fuel efficiency have been promoted in the automobile industry, the aviation industry, and the like. Among them, in order to reduce the weight of the car body and the airframe, the replacement of metal with fiber reinforced resin is expected, and the attention is increasing.
The resin used for the fiber reinforced resin is a thermoplastic resin or a thermosetting resin, and the fiber reinforced resin is a resin in which fibers are reinforced with these resins. Fiber reinforced plastics can be molded and molded by heating, have high productivity, are easy to perform secondary processing such as welding, have electrical insulation, are not corroded, and are excellent in recyclability. It is widely used in various fields due to its characteristics.
In addition, carbon fiber reinforced resin that uses carbon fiber as fiber is lightweight, has high strength and high rigidity, so it includes the automobile industry and aviation industry mentioned above, the shipping industry and space field, wind power generation, sporting goods, etc. , Applied research has been conducted in a wide range of fields and has already been used.

As an example of a molded product of fiber reinforced resin, a fibrous reinforcing material such as glass cloth or carbon fiber is impregnated with a thermosetting resin such as epoxy, phenol, or polyester in which additives such as a curing agent and an adhesive are mixed. The prepreg, which has been heated or dried to a semi-cured state, is cured by heating and pressurizing.
Processing of fiber reinforced plastic includes autoclave molding, oven molding, press molding, RTM / VaRTM method, pultrusion molding, filament winding, sheet winding, etc. Among them, high-quality fiber reinforced resin molded products with high productivity. It is said that press molding is desirable from the viewpoint of obtaining the above.

However, fiber reinforced plastics have less malleability than metals, and when press-molded at the same speed as metals such as iron, they break or wrinkle. Further, if too much heat is applied to the prepreg for molding, the viscosity of the resin decreases too much, the resin melts, and a clean molded product cannot be formed, and the viscosity does not decrease unless heat is applied. , There was a problem that molding was defective.

In response to such a problem, as a method for adjusting the fluidity of the prepreg resin composition, Patent Document 1 states, "A mixed epoxy of 50 to 90 parts by weight of a solid epoxy resin and 10 to 50 parts by weight of a liquid epoxy resin. It contains a resin, a rubber, and a curing agent, and the rubber is blended in an amount of 5 to 60 parts by weight based on 100 parts by weight of the mixed epoxy resin, and the curing agent is blended in an amount of 1 to 60 parts by weight based on 100 parts by weight of the mixed epoxy resin. A resin composition for a prepreg "containing 100 parts by weight" is disclosed (Patent Document 1: Japanese Patent Application Laid-Open No. 2005-213352).

Further, Patent Document 2 states, "Prepreg and heating using an epoxy resin composition which is excellent in storage stability at room temperature, can be heat-cured at a relatively low temperature and in a short time, and the cured resin has high heat resistance. Excessive flow of resin during pressure curing can be suppressed. ”A prepreg composed of a reinforcing fiber and an epoxy resin composition suitable for press molding, particularly high cycle press molding, is disclosed (Patent Document 2: Patent No. 2). No. 5682837).

Japanese Unexamined Patent Publication No. 2005-213352 Japanese Patent No. 5682837

The prepreg disclosed in Patent Document 1 and Patent Document 2 adjusts the fluidity of the resin according to the composition of the resin composition of the prepreg, and is effective only in the case of the resin composition having the disclosed composition. It will be demonstrated. That is, the problem is not solved for a prepreg using a resin composition other than the above composition (for example, a prepreg having a general composition). In recent years, it is not always possible to use the above-mentioned limited resin compositions for fiber-reinforced resin molded products used in various fields due to their uses, shapes, sizes, required costs, and the like. It is difficult to apply to all press moldings to meet increasing needs.
Further, Patent Documents 1 and 2 are all prepregs of thermosetting resins, and there is no reference to thermoplastic resins.
Therefore, an object of the present invention is to provide a highly productive thermoplastic fiber reinforced resin press molding method that does not reduce quality and work efficiency.

As a result of diligent research, the present inventors have found a method for press-molding a fiber-reinforced resin to obtain a fiber-reinforced resin molded product having a high degree of perfection. That is, the present invention includes the following.
[1] By pressing one prepreg of a thermoplastic fiber reinforced resin, a plurality of laminated prepregs, or a plurality of laminated prepregs in which an adhesive or an adhesive resin sheet is arranged between the prepregs. , A method for producing a thermoplastic fiber reinforced resin molded product having a thickness of 0.2 to 5.0 mm, in which the upper mold and the lower mold are heated, and the temperatures of the upper mold and the lower mold are set to 170. A step of adjusting to ~ 270 ° C., a step of arranging the prepreg between the upper mold and the lower mold, and a step of lowering the upper mold so that the upper mold and the lower mold are at 170 to 270 ° C. In the temperature range of, the step of deforming the prepreg by applying a load to the prepreg with the upper mold and the lower mold, and the temperature of the upper mold and the lower mold are measured per minute. The step of lowering the temperature at a speed of 5 to 50 ° C. and the step of raising the upper mold and taking out the thermoplastic fiber reinforced resin molded product after the upper mold and the lower mold are sufficiently cooled. Including, method.
[2] The thermoplastic fiber reinforced resin is polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyvinyl acetate, polyurethane, Teflon (registered trademark), acrylic, polyamide, polyacetal, polycarbonate, polyether, polyester, or a combination thereof. The method according to [1], which is a fiber-reinforced resin.
[3] The temperature of the upper mold and the lower mold is maintained at 170 to 270 ° C. for 0.3 to 2 minutes per 1 mm of the thickness of the prepreg when the upper mold is at the bottom dead center position. The method according to [1] or [2], further comprising a step.

According to the present invention, the thermoplastic fiber reinforced resin can be press-molded by appropriate temperature control and appropriate pressure control, and a highly accurate thermoplastic fiber reinforced resin molded product can be produced.

It is sectional drawing for demonstrating the press molding of the fiber reinforced resin which concerns on this invention. It is sectional drawing for demonstrating the press molding of the fiber reinforced resin which concerns on this invention. It is sectional drawing for demonstrating the press molding of the fiber reinforced resin which concerns on this invention. It is a graph which shows the change of the die temperature and the load at the time of a press which concerns on an Example.

A mode for carrying out the present invention will be described in detail with reference to the figures of Examples. The present invention is not limited to the examples, and the design can be appropriately changed within a range well known to those skilled in the art.
In the present specification, the fiber-reinforced resin molded product is a prepreg obtained by impregnating and drying a fiber bundle, for example, a fiber bundle such as a carbon fiber or a glass fiber with a thermoplastic resin or a thermosetting resin, and curing the prepreg by heating and cooling. The thermoplastic fiber-reinforced resin molded product is a molded product obtained from the above, and the resin is composed of a thermoplastic resin among the above-mentioned fiber-reinforced resin molded products.
Further, in the present invention, the thermoplastic fiber reinforced resin molded product is composed of a thermoplastic resin and a resin composition containing one of them.
Examples of the thermoplastic resin include polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyvinyl acetate, polyurethane, Teflon (registered trademark), acrylic, polyamide, polyacetal, polycarbonate, and polyether (polyester ether ketone, polyether ketone, etc.). Polyether sulfone etc.), polyester or a combination thereof and the like. These may be used alone or in combination of two or more.

[About press molding of thermoplastic fiber reinforced resin]
In the press molding of the thermoplastic fiber reinforced resin according to the present invention, the prepreg 3 of the thermoplastic fiber reinforced resin is press-molded to produce a molded product of the thermoplastic fiber reinforced resin.
As shown in FIG. 1, the apparatus for producing the thermoplastic fiber reinforced resin molded product according to the present invention by pressing is paired with the concave upper die 1 arranged above and the upper die 1. Includes a convex lower mold 4.
The concave shape of the upper mold 1 is a female mold for molding the prepreg 3, and the convex shape of the lower mold 4 is a male mold with respect to the upper mold 1. Further, the upper mold 1 is provided with a heater 2 for raising the temperature of the upper mold 1, and the lower mold 4 is provided with a heater 5 for raising the temperature of the lower mold 4.

In the press forming method of the present invention, as shown in the manufacturing process diagrams of FIGS. 1 to 3, the upper die 1 and the lower die 4 are heated, and the temperatures of the upper die 1 and the lower die 4 are set to 170 to 270. A step of adjusting the temperature to ° C., a step of arranging the prepreg 3 between the upper mold 1 and the lower mold 4 (step a), and a step of lowering the upper mold 1 to lower the upper mold 1 and the lower mold 1. A step of deforming the prepreg by applying a load to the prepreg 3 with the upper mold 1 and the lower mold 4 when the temperature of the prepreg 3 is in the range of 170 to 270 ° C. The step of lowering the temperature of the lower mold 4 at a rate of 10 to 50 ° C. per minute (step d, Fig. 2) and the upper mold after the upper mold 1 and the lower mold 4 are sufficiently cooled. The step (e step FIG. 3) of raising 1 to take out the thermoplastic fiber reinforced resin molded product 3A is included. If necessary, the temperature of the upper mold 1 and the lower mold 4 is maintained at 170 to 270 ° C. at the position of the bottom dead center for 0.3 to 2 minutes per 1 mm of the thickness of the prepreg 3. A step (step c, FIG. 2) is further included. Here, a method incorporating a holding step will be described.
In this embodiment, the prepreg 3 uses a thermoplastic fiber reinforced resin prepreg composed of carbon fiber and polypropylene, but is not particularly limited.
Further, in this embodiment, the prepreg is made by Mitsubishi Chemical (twill weave, 0.23 mm per sheet), and a plurality of sheets are used so that the thickness of the finished thermoplastic fiber reinforced resin molded product is 1.6 mm. It was carried out by laminating. The technique disclosed in the present specification can be used for a thermoplastic fiber reinforced resin molded product having a thickness of 0.2 to 5.0 mm, and the thickness of the finished product is adjusted by the number of laminated prepregs. be able to. Further, when laminating the prepregs, an adhesive and / or an adhesive resin sheet may be arranged between the prepregs to increase the laminating strength of the prepregs (make it difficult for the prepregs to peel off from each other). As the adhesive resin sheet, for example, an acrylic adhesive or an acrylic adhesive resin sheet can be used, and it may be arranged between all the prepregs to be laminated, or between the prepregs. Of these, the adhesive resin sheet may be placed only where necessary.

A feature of the present invention is to set an appropriate temperature and pressure in the pressing process. First, before arranging the prepreg 3, the upper mold 1 and the lower mold 4 are heated, respectively. The rate of temperature rise of each mold by heating is not particularly limited, and is preferably 5 to 40 ° C./min, more preferably 10 to 30 ° C./min.

When the upper mold 1 and the lower mold 4 reach the set temperature, the temperature is maintained at that temperature. The temperature for molding is 230 ° C. in this embodiment. This holding temperature is a temperature close to the temperature for molding, and is a temperature at which the resin is softened between the upper mold 1 and the lower mold 4 and can be shaped by the prepreg 3 arranged later. The molding temperature and holding temperature are, for example, in the range from the melting point of the thermoplastic resin of prepreg 3 to the melting point of the thermoplastic resin + 100 ° C., and in one example, from the melting point of the thermoplastic resin to the melting point of the thermoplastic resin + 70 ° C. If the molding temperature or the holding temperature is too high, it causes burning or poor gloss of the thermoplastic fiber reinforced resin molded product, and if the holding temperature is too low, the fluidity of the resin deteriorates, which causes distortion or whitening.

Next, the prepreg 3 is placed in the lower mold 4 (step a). At this time, in FIG. 4, it is the position (1). At the time of (1) in FIG. 4, the mold is not in contact with the prepreg, and substantially no pressure is applied.

After arranging the prepreg 3, the upper mold 1 is lowered while maintaining the temperatures of the upper mold 1 and the lower mold 4. Soon, the upper mold 1 comes into contact with the prepreg 3 (position (2) in FIG. 4), and the upper mold 1 further descends to the bottom dead center (step c). The upper mold 1 reaches the bottom dead center, and the load reaches the maximum value (position (3) in FIG. 4).

After the upper mold 1 reaches the bottom dead center, the load and temperature are held in that state for a predetermined time. The retention time at bottom dead center is adjusted mainly by the thickness of the prepreg 3. Generally, the holding time is between 0.3 and 2 minutes per 1 mm of thickness of prepreg 3. In this embodiment, it is held for about 2 minutes in order to produce a 1.6 mm thermoplastic fiber reinforced resin molded product 3A. A more preferable time for holding is that if the holding time is short, heat is not transferred to the entire material, so that it is difficult to obtain a desired shape. In particular, the corner molding is inadequate. Further, if the holding time is too long, the fluidity and color tone of the resin will change.

The load of the upper mold 1 at the bottom dead center is not particularly limited, and is preferably 800 to 1500 KN, more preferably 900 to 1400 KN.

After the upper mold 1 holds the temperature and load at the bottom dead center position, the temperature of the molds (upper mold 1 and lower mold 4) is lowered at a predetermined speed (position (4) in FIG. 4). ). Specifically, the upper limit of the descent rate is usually 50 ° C./min or less, more preferably 40 ° C./min or less. The lower limit of the descent rate is usually 5 ° C./min or more, preferably 10 ° C./min or more. When the thermoplastic fiber reinforced resin molded product is formed by pressing as in the present invention, the temperature drop rate is very important because it affects the surface finish and inner surface strength of the finished product. If the descent speed is high, voids, sink marks, and flow marks may occur. In addition, if the descent speed is too low, it may cause burning and poor gloss. If the descent speed is appropriate, the above-mentioned problems do not occur, and the generation of residual stress can be suppressed.

When the temperature is lowered at the above speed and the temperature drops to the temperature at which the thermoplastic resin hardens, the pressurization of the upper mold 1 is stopped (position (5) in FIG. 4) so that the upper mold 1 is returned to its original position. (Step e), the thermoplastic fiber reinforced resin molded body 3A is removed from the upper die 1, and the press molding is completed.

When the press is continuously performed, the mold temperature does not need to be returned to room temperature, and may be, for example, 60 to 90 ° C. If the temperature is high to some extent, the time for reheating can be shortened and the energy required can be reduced.

With the above press, it is possible to press the thermoplastic fiber reinforced resin, which is more difficult to press than metal.

1: Upper mold 2: Upper mold heater 3: Prepreg 3A: Thermoplastic fiber reinforced resin molded body 4: Lower mold 5: Lower mold heater

Claims (3)

Thickness by pressing one prepreg of thermoplastic fiber reinforced plastic, a plurality of laminated prepregs, or a plurality of laminated prepregs by arranging an adhesive or an adhesive resin sheet between the prepregs. It is a method for producing a thermoplastic fiber reinforced resin molded product having a size of 0.2 to 5.0 mm.
A step of heating the upper mold and the lower mold to bring the temperature of the upper mold and the lower mold to 170 to 270 ° C.
The step of arranging the prepreg between the upper mold and the lower mold, and
The prepreg is lowered by lowering the upper mold and applying a load to the prepreg with the upper mold and the lower mold in a temperature range of 170 to 270 ° C. for the upper mold and the lower mold. And the process of transforming
A step of lowering the temperature of the upper mold and the lower mold at a rate of 5 to 50 ° C. per minute, and
A method comprising a step of raising the upper mold and taking out a thermoplastic fiber reinforced resin molded product after the upper mold and the lower mold have been sufficiently cooled. The thermoplastic fiber reinforced resin is a fiber reinforced resin of polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyvinyl acetate, polyurethane, Teflon (registered trademark), acrylic, polyamide, polyacetal, polycarbonate, polyether, polyester or a combination thereof. The method according to claim 1. Further, a step of maintaining the temperature of the upper mold and the lower mold at 170 to 270 ° C. for 0.3 to 2 minutes per 1 mm of the thickness of the prepreg when the upper mold is at the bottom dead center position. The method according to claim 1 or 2, which includes.

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